To facilitate XML query processing, several labeling schemes have been proposed, in which the ancestor-descendant and parent-child relationships in XML queries can be quickly determined without accessing the original XML file. However, all of these existing schemes have to relabel the existing nodes or recalculate certain values when order-sensitive updates cause insertions, thus causing the label update cost to be high. In this paper, we propose a novel labeling scheme, called IBSL (Improved Binary String Labeling), which supports order-sensitive updates without relabeling or recalculation. In addition, we reuse the deleted labels at the same position in the XML tree. The conducted experimental results show that IBSL efficiently processes order-sensitive queries and leaf node/subtree updates.